Project Summary: The exploratory research proposed here addresses the critical issue of understanding both macrostructure and microstructure of infant sleep as well as the role of sleep as a facilitator of brain maturation and cognitive outcomes. Although extensive research has been conducted on sleep in animal models, in adults and in premature neonates, very little is known about the neurophysiology of sleep in healthy human infants. Current research suggests that alterations in sleep pattern or duration play a role in almost all known psychiatric disorders and further, that many of the mechanisms governing developmental plasticity also mediate plasticity in the adult brain. Variability in sleep patterns is also gaining attention as a possible early biomarker for a number of neurodevelopmental disorders. Identification of reliable biomarkers could lead to targeted diagnostic tools that would be useful in diagnosing a number of developmental disorders. We will examine infant daytime sleep in a rarely studied age group (3, 6 and 9 months), using advanced dense-array EEG recording (dEEG) and analytic techniques seldom used in sleep studies, in combination with concurrent assessment of infant cognition and information processing. Thus, the aims of this application include: (1) characterizing the topographical spectral composition and network connectivity of non-rapid eye movement sleep (NREMS) and rapid eye movement sleep (REMS) in typically developing, napping infants, at 3, 6, and 9 months; and (2) testing the hypothesis that neurophysiological measures of topographical electrophysiology (microstructure) and temporal global functional networks (microstates) during NREMS are associated with cognitive measures. We propose to achieve these aims using dEEG data and characterizing spectral power, coherence, and network connectivity of NREMS and REMS as well as the morphology, topography, and developmental trajectories of two prominent NREMS waveforms (i.e. sleep spindles and slow waves), which are hypothesized to be critical to infant brain development. Finally we will use standardized cognitive scales and auditory and visual habituation/recognition-memory tasks to assess infants? cognitive development levels as well as working memory and attention. We anticipate that the outcomes of this study will accelerate our understanding of infant brain development across the first year of life, delineating the emergence, function and maturation of changing oscillatory sleep patterns, while simultaneously facilitating future translational approaches (e.g. interventional strategies for slow wave and spindle enhancement) targeting developmental sleep as it relates to the prevention of neuropsychiatric disorders.